Embodiments of the inventive concept relate to a data storage device, and more particularly, to a data storage device including a table that stores compression values for addresses input during a predetermined period as values for compensating for a shift in initial threshold voltage, a method of operating the same, and a data processing system including the same.
Memory devices used to store data may be divided into volatile memory devices and non-volatile memory devices. The characteristics of memory devices may vary with use environment, the number of uses, and/or a use time.
A flash memory device is an example of electrically erasable programmable read-only memory (EEPROM) in which multiple memory cells are erased or programmed in a single program operation. In a flash memory device using a floating gate technique, data retention characteristics and the number of program-erase (P/E) cycles with no quality deterioration, i.e., endurance, are critical issues in terms of reliability.
Charges or electrons stored in a flash memory cell in a flash memory device may be leaked from a floating gate through various failure mechanisms, such as thermal ion emission through a defective interpoly insulation film, charge diffusion, ion impurities, or program disturb stress. Such leakage would cause the decrease of a threshold voltage.
Repetitive P/E cycles put stress on memory transistor oxide films of flash memory cells, and this stress may cause failure in the flash memory cells. The threshold voltage of flash memory cells may shift (increase or decrease) due to such stress. For example, electrons may be leaked from floating gates of programmed flash memory cells. Accordingly, the threshold voltage distribution of programmed flash memory cells may shift toward lower voltage.
Initial threshold voltages of flash memory cells may have a finite distribution on the basis of processes and design targets. However, the distribution of the initial threshold voltages changes according to use environment, the number of uses, and/or use time. When a program operation or a read operation is performed on a memory device including flash memory cells, an initial threshold voltage distribution needs to be appropriately controlled. When the initial threshold voltage distribution is not appropriately controlled, the program or read operation cannot be appropriately performed on the memory device.